Recent evidence from our and other laboratories has shown that certain marine animals, notably sponges and coelenterates, are sources of a variety of new steroids, notably of sterols with unusual side chains as well as of 19-norsterols. In most instances, there are no terrestrial counterparts to these highly important substances and a program is proposed which involves a systematic search (using gas chromatography coupled directly with mass spectrometry and utilizing computer search as well as computer interpretation programs developed in our laboratory) for novel steroids from specified orders of marine animals. The structures of such novel compounds will be proved by synthesis and potential precursors for economic large scale syntheses of medicinally important steroid drugs will be identified. Since it is likely that most of the structurally new sterols are not produced by these marine animals but rather by precursors in the food chain or by symbionts, major emphasis will be placed on identifying the actual organism responsible for the biosynthesis of such steroids. Work will be performed on elucidating the biological role and biosynthesis of these novel steroids with major emphasis on 19-nor steroids (because of their obvious importance in areas such as oral contraceptives), cyclopropane-containing sterols (only marine sterols have so far been encountered bearing a cyclopropyl ring in the side chain) and 24-nor-C26 sterols, which are also unique to the marine world. Extensive synthetic work is envisaged as well as methodological advances on further improving separation and detection techniques for sterol mixtures, since these should be of utility in many other biomedically significant areas dealing with steroids. As an example of the importance of such separation and detection techniques, one can cite our recent isolation and characterization of nearly 50 steroids from only a single marine soft coral.